My unpleasant lesson learned from traveling on airlines which are very flexible (SQ and AA but also BA) vs my old UA/LH/LX experience is that if you are proactive as a passenger, monitor departures and delays, and check for alternative routings you reliably end up with a disaster.

You will be stranded at an airport which is not on your ticketed route, no one will be in charge of you, it will be impossible to point at a guilty airline or person. I learned in my UA days that fixing problems makes additional heads of the serpent grow and I have to re-learn it for OneWorld.

This is yet another example where the "I can't be bothered" attitude would have saved the OP a lot of headache.